1. Field of the Invention
The invention relates to a denture cleansing composition which does not contain enzymes and can effectively remove stains similar to known denture cleansing formulations, and a process for making such a composition. The composition also exhibits longer lasting fragrance retention over known denture cleansing formulations. This is especially true for those who soak their dentures overnight.
2. Description of the Related Art
Denture cleansing generally is carried out either by brushing dentures with a paste or by soaking dentures overnight in an aqueous cleansing solution. Aqueous denture cleanser solutions are known and generally compose tablets, granules, or powders that are dissolved in water to form a cleansing bath or cleansing system in water.
Denture cleansing compositions, such as effervescent tablets and powders, are well known in the art. Traditionally, these compositions have contained a variety of sulfate salts, such as bisulfates, monopersuifates, and sulfates as detergents, oxidizers and the like, and have also utilized alkali metal and alkaline earth metal halides as bleaches. Such compositions have also included perborate, carbonate and phosphate salts in varying amounts to provide effervescence and activation. Representative examples of cleansing compositions covering these various materials are set forth in U.S. Pat. Nos. 3,337,466, 3,704,227, 4,362,639 and 4,857,224.
The cleansing systems produced by these compositions when dissolved in water have drawbacks. The pH of the aqueous solution is too low (i.e. too acidic) for the retention of fragrances. In addition, the reaction of monopersulfates in the compositions with chlorides in the water produces a hypochlorite which reacts with expensive fragrances in the compositions, depressing their efficacy. Moreover, known denture cleansers can be formulated to provide an initial fragrance level when the cleanser is in a tablet form, but they cannot be formulated to maintain the level of fragrance upon dissolution without compromising the hardness of the tablet, or maintain the level of fragrance when the resultant solution is allowed to stand overnight.
The fragrance of a denture cleaning composition in aqueous solution is an important feature. The sweet or pleasant odors which emanate from the compositions are due to the introduction of ingredients such as oils. The presence of a fragrance is aesthetically pleasing to a consumer, as well as an indicator to a consumer that a product works effectively. Consumers are more likely to purchase a denture cleanser characterized as having longer fragrance retention levels. This is especially true for those who soak their dentures overnight.
In addition, many denture cleansing compositions feature the use of alkaline proteolytic enzymatic cleansing agents. The use of enzymes in denture cleansing compositions, however, has many drawbacks. The pH of the aqueous solutions of many systems is too low for fully effective cleaning enzyme activity. Also, the reaction of the monopersulfate in the compositions with chlorides in the water produces hypochlorite which inactivates the cleaning enzymes in the compositions, further depressing their efficacy.
Moreover, the use of enzymes is expensive. The high cost of using enzymes is due not only because the enzymes themselves are expensive, but also because manufacturing facilities must be especially designed to safely incorporate and handle enzymes. This is particularly true in the United States where stringent governmental regulations require special equipment and operating procedures which increases not only the ultimate cost of manufacturing denture cleansing compositions, but also increases the time which is required to produce these compositions.
There have been efforts, with limited success, to develop a denture cleansing compositions that do not comprise the use of enzymes and in which fragrance instability does not occur, while still providing good denture cleaning efficacy.
U.S. Pat. No. 4,409,118 to Anthony Eoga, issued Oct. 11, 1983, discloses an effervescent cleansing composition in tablet form comprising: (1) a phosphate salt; (2) a silicate salt; and (3) at least one perborate salt. At least part of the perborate salt is in a compacted granulated mixture with a polymeric fluorocarbon.
U.S. Pat. No. 4,857,224, to Anthony Eoga, issued Aug. 15, 1989, discloses an effervescent cleansing composition in tablet form comprising: (1) a pregranulated and compressed mixture of an anhydrous perborate, a perborate monohydrate and a polymeric fluorocarbon compound, and (2) a monopersulfate compound. This composition is useful for forming a tablet from monopersulfates and anhydrous perborates.